In the area of industrial adhesives, hot melt adhesives are commonly used to bond together a wide variety of articles including labels to containers and disposable absorbent articles comprising non-woven substrates e.g. adult incontinence products, disposable diapers, sanitary napkins, bed pads, puppy pads, medical dressings, etc.
Hot melt adhesive compositions often include a polymer and a tackifying agent, and in some cases wax or oil. Styrene block copolymers have been used as a polymer in such compositions.
Melt flow rate (MFR) is inversely related to the viscosity of a polymer. A higher MFR means that a polymer has a lower viscosity. Commercially available styrene block copolymers (SBC) work well in adhesives, but are not commonly commercially available with a high melt flow rate (i.e. >than 15 g/10 min (190° C., 2.16 kgs)). The grades that are available, often achieve the high melt flow rate with a high di-block content which can lower the mechanical properties of the polymer. This makes it difficult to formulate a low application temperature hot melt adhesive with good mechanical properties.
It would be desirable to be able to formulate a low application temperature hot melt adhesive based on SBC, with good mechanical properties. It would further be desirable to be able to formulate a hot melt adhesive with a higher amount of SBC, while maintaining a low viscosity.